1. Field of the Invention
The present invention relates to a VoIP technique, and more particularly, to a method of detecting the type of network address translator (NAT).
2. Description of the Related Art
With developments in the field of networking technology, the voice over IP (VoIP) technique is gaining importance due to the relatively low costs associated with web-based telephone services. Web-based telephone services have the potential to replace traditional telephone services. On the Internet, connection to a terminal device is provided through a distributed IP address. However, there are a limited number of public IP addresses. Consequently, a network address translation (NAT) technique has been developed to solve this problem. Many computer devices therefore utilize a NAT apparatus to connect to the Internet. In other words, these computer devices individually have a private IP address internally, and the NAT apparatus uses a public IP address to connect externally with the Internet.
Due to requirements imposed by the NAT apparatus for external connectivity, when these computer devices utilize the private IP address to perform communications over a VoIP connection, the connection fails in the networking communications environment. This failure occurs because the computer device cannot establish a real-time protocol connection utilizing the private IP address. A current solution to this problem involves utilizing a STUN technique. As shown in FIG. 1, a practical environment of such a technique includes a STUN client 11, and two STUN servers 12, 13. This technique requires an independent communication protocol; the steps required to perform the technique are quite long (requiring four tests), and only the STUN client 11 can obtain the network type. However, in a practical application, this technique needs to modify or augment another communication protocol to send a detection message to a proper server. Furthermore, this technique requires additional establishment costs for the STUN servers 12,13.
Therefore, it is desirable to provide a method of detecting the type network address translator to mitigate and/or obviate the aforementioned problems.